Urban water future: Changing climate means changing water

Monday , March 30, 2015 - 12:00 AM

Editor’s note: This is the final in a three-part series exploring the vital issue of Utah’s urban water supplies. The first story delved into aging infrastructure and the second story addressed conservation efforts.

The T.W. Daniel Experimental Forest, located about an hour up Logan Canyon from Utah State University, is full of all kinds of shiny metal objects.

The metal feathers of rain gauge windscreens rattle with the breeze. Mylar insulation wraps trees, which helps measure sap flux and how conifers transpire water. All kinds of sensors and instruments measure soil moisture, snow water equivalent and weather, then transmit the data down to the valley below.

The majority of Scott Jones’s instruments are kept in a small plot, around 200 by 400 yards, but they’re adding to the volume of information helping scientists build better climate models. Those models, in turn, will help water managers have a better idea of what to plan for with a changing climate.

“We’ve seen a lot of rain this year, which is unusual,” Jones said, who works as a professor of environmental soil physics at Utah State. “So that’s one of the questions we’re interested in … what’s going on with the transition between where it’s raining and where it’s snowing? That can be a big factor in the water that’s delivered to the reservoirs.”

It was a weird and warm winter in northern Utah. By mid-March, the T.W. Daniel Experimental Forest was still only accessible by snowmobile, but snowpack sat at only 75 percent of normal.

A big water shift is coming to the West, and both researchers and policymakers want to know what it means for Utah. Jones’s research at the Experimental Forest is part of iUTAH, or “innovative Urban Transitions and Aridregion Hydro-sustainability, a five-year collaboration among universities, government and other interested parties to monitor water on a large scale in the state. Sites are set up on Red Butte Creek in Salt Lake, the Provo River in the Heber Valley and on the Logan River.

As it turns out, looking at things as small and localized as the soil, snow and trees on a tiny plot in Logan Canyon helps researchers understand a lot about our region’s water and the larger global climate system.

Back at the university, situated at the mouth of the canyon just above the Logan River, researchers at the Climate Center are using this site-specific data to fine-tune climate models and make forecasts about future water supplies. They’re also on a mission to educate the public and policymakers, providing clarity in a torrent of information about climate change.

“The trend is definitely upward in terms of coming to grips with the notion that the climate is changing and humans are driving that change,” said Robert Davies, an extension climatologist at the Climate Center. “Within the state of Utah, there are many, many people who accept it; certainly Utah’s scientific community does en masse.”

Before he can explain the future implications of climate change on northern Utah’s water supply, Davies said it’s important to first wrap one’s head around the complexities at play — what researchers know, what they don’t know and why that’s important.

“It’s important because the science has profound implications for public policy,” he said. “There’s so much conflicting information from the media … Let’s just say that if you’re confused about it, you have every right to be.”

Ebbs, flows and tides

Davies said that when most people think about the word “climate,” they associate the term with “average weather.” But when scientists talk about climate change, they’re really talking about two kinds of change, in variability and trend.

Davies compares the two changes to standing on a beach, watching the ocean.

“As the waves come in, some come higher than others, and that’s the variability in the water level in the short-term,” he said. “Contrast that with a trend, which is the tide coming in, and that happens over a longer period.”

An observer on the beach experiences both waves and tides at the same time. The trick is sorting out the two.

“They have different mechanisms, and different things that cause them,” Davies said. “From a climate science perspective, you’re trying to untangle what’s happening in the climate is as of the variability, or a natural oscillation of the climate cycle, and what’s part of the trend.”

Scientists have a good grasp of the tide, or trend. It’s global warming, caused by a build-up of greenhouse gasses that doesn’t let energy escape the planet, leading to an overall warming of the planet.  Figuring out what’s behind the variability of climate change is trickier. Scientists are still sorting out the waves from the tide from their location on the shore.

“Variability has to do with how the Earth’s system redistributes energy,” Davies said. “So energy comes in from the sun, it gets warmer in the tropics than at the poles, and the Earth’s system redistributes that energy.”

A big part of that redistribution comes from currents and circulations in the atmosphere. Another big piece of energy distribution comes from the ocean, and those cycles all operate on different time scales.

“With the atmosphere, it’s hours to weeks,” Davies said. “With the oceans, it’s more like once in a millennium.”

Between those cycles, there are other cycles that interact and happen at timescales lasting from decades to centuries.

“What we find is that things happening on a cyclic value in some parts of the world will affect you in other parts of the world,” Davies said.

Circulating water

To understand all those interacting cycles and how they influence a small portion of the globe, Davies has another comparison. Utah is like a hole in a golf course, and an atmospheric cycle is like turning on a sprinkler, which moves water in a circle.

“So you’ve got wet cycles and dry cycles, wet and dry,” he said.

More sprinklers turn on, operating at different speeds. Sometimes the sprinklers overlap the hole at the same time, sometimes none are cycling water into the hole as they water other parts of the course.

Like the hole on a putting green watered by multiple sprinklers, Utah’s precipitation cycles arise from cycles in the oceans and atmosphere, often thousands of miles away. These “climate oscillations" arise from the redistribution of energy from equator to poles. (Image courtesy Utah Climate Center)

“By studying that over time, you can start to back out and say ‘I think there are three cycles going on,’” Davies said.

By studying these overlapping cycles, scientists can also figure out where the cycles are coming from and how long they take.

“There are different techniques for doing that, and this is a lot of what we do at the climate center, is tying natural cycles to Utah,” Davies said.

He noted three powerful cycles driving the state’s climate, influencing temperatures and the precipitation that fills our mountains, streams and reservoirs. One comes from the Western Pacific, with oscillations in sea surface temperature. Another comes from oscillations in air pressure over the Arctic and another comes from the Atlantic.

Climate change, arising from an imbalance of energy entering the Earth system (less energy leaving than entering) can have an effect on cycles, changing their intensity, their duration, even creating new cycles — like changing how quickly the sprinklers rotate, how often they turn on, and how much water flows through them. (Image courtesy Utah Climate Center)

“All of these things happen on different timescales, typically years to decades, but they’re cyclic,” Davies said. “Once you understand the cycle and mechanism by which the change over there affects you over here, you can make quite long-term projections, which we’ve done.”

What trees tell us

To boost those projections, climate scientists have also delved into the past. Using tree rings from sites throughout the state, they’ve mapped northern Utah’s climate past, back 1,000 years. The tree rings give scientists a sense of the area’s natural climate variability before human activity started forcing a global warming trend.

As determined by tree ring analysis, northern Utah droughts of the 20th century, particularly the late 20th century, are mild in both depth and duration when compared to those of the past 800 years. Periods considered “drought”  by 20th century standards are shaded orange. (Courtesy Utah Climate Center)

“Most of this, let’s say before 1900, is natural variability in the precipitation climate of northern Utah prior to significant greenhouse gas impact,” Davies said. “So there’s no real global climate trend going on here, it’s just what happens based on redistribution of Earth’s energy and what it does to precipitation patterns in northern Utah.”

In other words, tree ring records show which sprinklers have been watering our part of the putting green in Utah, and how long it takes them to cycle. The records also show some long periods of drought, in some cases lasting decades. The period including the 20th century, however, has been unusually wet.

Dendrochronologist with the U.S. Forest Service Justin DeRose shows off some of the douglas fir and Utah juniper samples they have brought back to study at the dendrochronology workspace at Utah State University on Friday, March 13, 2015. A measuring tape along the edge of the table captures patterns in tree rings to help identify the years of each ring. This information can be used to identify years of excess rain and drought. (Briana Scroggins/Standard-Examiner)

“So here’s the question. Are we on the extreme edge of the this natural variability and we can expect to plop back?” Davies said. “Or is the 20th century wetter because of a changing climate?”

When the Earth’s entire climate system changes, it doesn’t just change the averages in temperature and precipitation, it changes the variability, or extremes, as well.

“This part of the globe, the North American West, and the Western U.S. in particular, turns out to be particularly difficult to make projections for,” Davies said. “What that tells us is we’re missing key features. There are sprinklers out there we don’t know about.”

How water will come in northern Utah

Scientists do know the trend. Utah is getting warmer. That means the southern portion of the state will get drier. The variability in northern Utah is a challenge, however. A different set of sprinklers is hitting the area, which means the northern precipitation picture remains unclear.

It might get drier, or it might get wetter. One thing’s clear, however — warmer temperatures mean less water delivered as snow, and more water coming as rain. Warmer temperatures also mean more evaporation, more water in the atmosphere and more intense storm events.

“Here in Logan, we get 30 inches of precipitation a year,” Davies said. “It’s a big difference if we get around three inches every month, or 30 inches in two weeks. It’s still the same amount every year, but how it comes is hugely important.”

For water managers, both the region’s history of drought and our climate future are concerning prospects.

“What it points to is, our need for storage will be greater than it is today,” said Tage Flint, general manager at Weber Basin Water Conservancy District, which operates the seven dams and reservoirs feeding Weber, Davis, Morgan, Summit and parts of Box Elder counties.

Past tree ring data means the region could see long, unprecedented drought, and more water storage will be vital to see Utah residents through. Future climate change means water will no longer be stored in the mountains, as snow, gradually melting off in the summer as consumers need it.

Eric Millis, director of the Division of Water Resources, said climate change in the state also points to a need to look at new water sources.

“I know people beat on the Bear River development and Lake Powell Pipeline, but those two projects bring in water from another basin into Davis, Weber and Salt Lake counties, as well as Washington and Kane counties,” he said. “The projects will help diversify some of the supplies they have.”

Conservation, too, will be key. And if northern Utah does experience the prolonged drought periods shown by old trees, yards and gardens in the region could look very different.

“If we’re just watching the climate get drier and drier, and we have longer droughts than those we experienced in the 20th century, we have no choice but to change landscaping,” Millis said. “We’ve always said we’d adaptively manage, and we hope things will change slowly enough so we can recognize what’s happening and change with it.”

That’s where the models come in. The better scientists understand the cycles and oscillations influencing precipitation in the West, the more planning tools they can provide for water managers.

“We’re trying to get the best models moving forward to plan our supply around,” Flint said. “The extremes of some of those things are outside the realm of our planning, but as we get this new data we try to incorporate it into our water supply options.”

At the T.W. Daniel Experimental Forest, Jones’s research will help further refine those climate models. Mountain landscapes, like Logan Canyon, have a lot of variability compared to flatter terrain. Variability in land surface and vegetation interacts with the atmosphere, and can muddle with human-made models. The more site-specific data researchers gather in Utah, the better our climate models become.

“In terms of questions of climate change, we’re just getting data for that, with this system we have about six years of data,” Jones said. “That’s probably not enough to say a lot about climate change, but certainly, we have seen big changes in precipitation up here.”

But scientists need a long record to get good statistics on climate, and iUTAH funding for the experiment forest study is set to run out in two years.

“Who’s going to continue to fund the maintenance of this hardware? That’s (another) big question we don’t know the answer to,” Jones said. “Hopefully the state of Utah will see the value in maintaining that system.”

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